R/add_gps_to_rayshader.R

In geoviz: Elevation and GPS Data Visualisation

#' Adds a GPS trace to a 'rayshader' scene
#'
#' @param raster_input a raster
#' @param lat vector of decimal latitude points
#' @param long vector of decimal longitude points
#' @param alt vector of altitudes
#' @param zscale ratio of raster cells to altitude
#' @param line_width line width of the gps trace
#' @param colour colour of the gps trace
#' @param alpha alpha of the gps trace (has no effect if lightsaber = TRUE)
#' @param lightsaber (default = TRUE) gives the GPS trace an inner glow affect
#' @param clamp_to_ground (default = FALSE) clamps the gps trace to ground level + raise_agl
#' @param raise_agl (default = 0) raises a clamped to ground track by the specified amount. Useful if gps track occasionally disappears into the ground.
#' @param ground_shadow (default = FALSE) adds a ground shadow to a flight gps trace
#' @param as_line (default = TRUE) Set to FALSE to render single points instead of a trace line (which then ignores line_width & lightsaber)
#' @param point_size size of points when as_line = TRUE
#'
#' @return Adds GPS trace to the current 'rayshader' scene
#'
#' @examples
#' flight <- example_igc()
#' add_gps_to_rayshader(example_raster(),
#'   flight$lat,
#'   flight$long,
#'   flight$altitude,
#'   zscale = 25)
#'
#' @export
add_gps_to_rayshader <- function(raster_input, lat, long, alt, zscale, line_width = 1, colour = "red", alpha = 0.8, lightsaber = TRUE, clamp_to_ground = FALSE, raise_agl = 0, ground_shadow = FALSE, as_line = TRUE, point_size = 20){

  coords <- latlong_to_rayshader_coords(raster_input, lat, long)

  distances_x <- coords$x

  distances_y <- coords$y


  if (clamp_to_ground | ground_shadow) {

    sp_gps <- sp::SpatialPoints(cbind(long, lat), proj4string = sp::CRS('+init=epsg:4326'))

    sp_gps <- sp::spTransform(sp_gps, sp::CRS(as.character(raster::crs(raster_input))))

    gps_ground_line <- raster::extract(raster_input, sp_gps)

  }

  if(clamp_to_ground){

    track_altitude <- gps_ground_line

  } else {

    track_altitude <- alt
  }

  if(as_line){

    if(!lightsaber){
      rgl::lines3d(
        distances_x,  #lat
        track_altitude / zscale,  #alt
        -distances_y,  #long
        color = colour,
        alpha = alpha,
        lwd = line_width
      )
    } else {

      #render track 3 times with transparent & thicker outside

      rgl::lines3d(
        distances_x,
        track_altitude / zscale,
        -distances_y,
        color = colour,
        alpha = 0.2,
        lwd = line_width * 6,
        shininess = 25,
        fog = TRUE
      )

      rgl::lines3d(
        distances_x,
        track_altitude / zscale,
        -distances_y,
        color = colour,
        alpha = 0.6,
        lwd = line_width * 3,
        shininess = 80,
        fog = TRUE
      )

      rgl::lines3d(
        distances_x,
        track_altitude / zscale,
        -distances_y,
        color = lighten(colour),
        alpha = 1,
        lwd = 1,
        shininess = 120
      )

    }

    if(ground_shadow){
      rgl::lines3d(
        distances_x,
        gps_ground_line / zscale + raise_agl,
        -distances_y,
        color = "black",
        alpha = 0.4,
        lwd = line_width * 2,
        shininess = 25,
        fog = TRUE
      )
    }
  } else {

    rgl::points3d(
      distances_x,  #lat
      track_altitude / zscale,  #alt
      -distances_y,  #long
      color = colour,
      alpha = alpha,
      size = point_size
    )
  }
}